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Table of Contents ☑ ☐ UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 OR TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number : 0-18415 Isabella Bank Corporation ( Exact name of registrant as specified in its charter ) Michigan ( State or other jurisdiction of incorporation or organization ) 38-2830092 ( I.R.S. Employer identification No. ) 401 North Main Street , Mount Pleasant , Michigan 48858 ( Address of principal executive offices ) ( Zip Code ) Registrant's telephone number , including area code ( 989 ) 772-9471 Securities registered pursuant to Section 12 ( b ) of the Act : Title of each class None Trading Symbol ( s ) N / A Name of each exchange on which registered N / A Securities registered pursuant to Section 12 ( g ) of the Act : Common Stock - No Par Value ( Title of Class ) ☑ No Indicated by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . □ Yes Indicated by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . □ Yes ☑ No Indicate by check mark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . × Yes No Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( §232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . ☑ Yes □ No Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a smaller reporting company , or an emerging growth company . See definition of " large accelerated filer " , " accelerated filer " , " smaller reporting company " and " emerging growth company " in Rule 12b - 2 of the Exchange Act . Large accelerated filer Non - accelerated filer ☐ ☑ ☐ ☑ Accelerated filer Smaller reporting company Emerging growth company ☐ If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . ☑ Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . □ Yes > No The aggregate market value of the voting stock held by non - affiliates of the registrant was $ 139,668,000 as of the last business day of the registrant's most recently completed second fiscal quarter . The number of common shares outstanding of the registrant's Common Stock ( no par value ) was 7,955,620 as of March 9 , 2021 . DOCUMENTS INCORPORATED BY REFERENCE ( Such documents are incorporated herein only to the extent specifically set forth in response to an item herein . ) Portions of the Isabella Bank Corporation Proxy Statement for its Annual Meeting of Shareholders to be held May 4 , 2021 are incorporated by reference in this Form 10 - K in response to Part III . The Isabella Bank Corporation Proxy Statement will be mailed on or before March 26 , 2021 . 1